The invention relates to a wet metallurgical process using at least one gaseous reactant and a closed system.
Wet metallurgical processes play an important part in the processing of ores for recovery of metals. The steps of the process including mixing, suspending, grinding, reacting as well as material- and heat-exchange of solid, liquid, and gaseous phases with one another.
A combination of these steps produces precipitation of metals, as for example copper or nickel by means of hydrogen, for example according to the equation: EQU Cu.sup.2+ + H.sub.2 .fwdarw. Cu.degree..dwnarw. + 2H.sup.+
the precipitation of a metal salt progresses for example according to the reaction equation: EQU H.sub.2 S + Cu.sup.+ .fwdarw. Cu.sub.2 S.dwnarw. + 2H.sup.+
of importance also are further oxidation procedures which progress for example according to one of the following equations: EQU 2H.sup.+ + Fe.sup.2 + 1/2O.sub.2 .fwdarw. Fe.sup.3+ + H.sub.2 O EQU znS + H.sub.2 SO.sub.4 + 1/2O.sub.2 .fwdarw. ZnSO.sub.4 + S.degree..dwnarw. + H.sub.2 O
frequently also metallurgical processes include solution reactions of which the following is an example: EQU ZnO + H.sub.2 SO.sub.4 .fwdarw. ZnSO.sub.4 + H.sub.2 O
in some of these processes, pressures of 10 to 100 atmospheres are used as well as high temperatures. A primary problem in carrying out such methods resides in bringing reactants of different phases into intimate contact. For example in oxidation reactions, the speed of diffusion of the gas (oxygen) through the liquid is the speed-determining factor for progress of the reaction. This is true also for the diffusion of hydrogen gas in precipitation procedures or for mixing- or reduction-gases in reduction procedures.
The German Laid Out Specification No. 1,038,762 discloses use of a pulsating agitation for the lixiviation of sulfidic ores. An electromagnetic driving system is disclosed as well as an agitating member of corrosion-resistant material. System cost is substantial and the device furthermore is relatively delicate or sensitive for such a rough operation. Thus the disclosed device is not entirely satisfactory.
Another agitation device for pressure-lixiviation, developed by the firm of Sherrit-Gordon, divides the oxygen in large, temperizable agitating-autoclaves by means of propellers in the electrolyte. This procedure depends upon the speed of rotation of the propeller and is therefore limited. Another method for the smelting of complex sulfidic ores by a wet method suggested in the German Pat. No. 888,929 includes guiding the stream of oxygen in circulation through the ore-suspension.
Also known for use in the lixiviation of copper-grit-concentrates is a vessel filled with steel balls, whereby the balls are moved by means of a central agitator assembly. A gas introduced through the agitator assembly into the electrolytes is divided very finely. Such device has high power requirement, correspondingly heavy wear, and relatively low output, preventing application on a large scale.
The so-called Pachuca-tank is known for an agitation-lixiviation process, in which a gas/liquid-reaction takes place. In the impeller-agitating assembly of the tank, an agitator is arranged in a central conducting pipe which causes a mixture of the gas with the liquid.
None of the known apparatus are qualitatively or quantitatively satisfactory for use at high pressures and/or high temperatures.
Some electrochemical reactions present other difficulties, as for example in the depositing of copper from copper sulphate by means of electron-exchange with iron. During the reaction, layers form on the reactants which hinder the diffusion steps, or in extreme cases stop the reaction entirely.
Reaction-grinding is known for overcoming this difficulty, for example in a ball mill. By allowing leaching of liquid into the solid material, appreciably shorter grinding periods are required for any desired degree of grinding. In lixiviation processes the times are also appreciably decreased, because by means of the grinding fresh, reactionable surfaces are exposed to contact with the liquid solvent.
Bodies or balls used for their catalytic effect are suggest in the German Laid Out Specification No. 1,203,746. More intensive reactions are achieved for example, if iron is added as a ferro- or ferri-combination. No such metallurgical processes are known to have been employed by which a gas is reacted with solid any/or liquid phase reactants. In this connection, the rate of passing of a gas into a liquid in solution or suspension therewith determines the speed of the reaction.
Several principles are known in the art to bring gases and liquid into solution and to speed their reactions with substances dissolved or finely distributed in the liquid. The gas present may be finely distributed as an emulsion in the liquid to have form as large a surface as possible between the phases. An increase in pressure will increase the solubility and decrease the gas volume in the liquid. Third, an increase in temperature reduces solubility of the gas in the liquid and increases the reaction speed of the dissolved or finely distributed solid substances with the gas.
All known systems which attempt to mix gases intimately with a liquid by spraying or stirring are only partly satisfactory. The spraying of gases is limited in effectiveness by a low intermixing effect; in addition the size of the gas bubbles is dependent on the cross-section of the nozzles and the spraying pressure. Also with a stirring system, the mixing effect of the gas with the liquid is limited by occurrence of a suction-funnel about the stirrer, so an increase in the speed of stirring above a certain limit no longer improves the distribution of gas.
The object serving as basis for the invention is to improve upon the known methods for carrying out wet metallurgical processes. It is particularly sought to make possible, through a simple apparatus without size or sealing problems, the use of high pressures and/or temperatures.